This invention generally pertains to light reflectors. More specifically, the present invention relates to a light reflector assembly for use in dental or medical lighting devices in which a selectively detachable cover plate overlies a rear surface of a glass substrate.
The invention is particularly applicable to a dental light reflector in which a coating on a rear surface of a glass substrate has flaked off or peeled off. In accordance with the invention, a separate cover plate can then be secured over the substrate to put the light quickly and inexpensively back into operation. However, it will be appreciated by those skilled in the art that the invention has broader applications and may also be adapted for use in many other environments where the reflection of light is important.
Glass reflectors have been adopted in the dental and medical fields in order to reflect visible light in a predetermined pattern which avoids shining light into the eyes of a patient and concentrates the light in the area of the body to be operated on. It has been thought desirable that ultraviolet and infrared light not be reflected back at the patient thereby providing a "cool" light. When a glass substrate of the reflector is coated with a dichroic coating, it will satisfactorily reflect a substantial portion of visible light while allowing infrared and other undesirable light to pass therethrough. The dichroic coating is generally provided on the rear surface of the glass substrate. However, such a coating on the rear surface of the substrate can be easily damaged by the cleaning or handling of the reflector.
Accordingly, the conventional design provides a protective layer of a PTFE (Teflon) paint over the dichroic coating on the rear surface of the glass substrate to aid in preventing damage to the coating. The paint coating layer is also utilized to diffuse light passing through the reflector thereby reducing undesirable glare from the rear of the reflector. Such a conventional reflector, however, provides a problem in that the protective diffuser paint coating on the rear surface of the glass substrate peels off after a period of use. This peeling also damages or destroys the dichroic coating on the rear surface of the substrate. Although it is not known for certain what causes such peeling, it is believed that one factor may be the tremendous temperature swings (e.g. from 25.degree. C. when the lamp is off to above approximately 150.degree. C. when the lamp is on) that the substrate and two coating layers are exposed to in combination with the differential thermal expansion rates of the several materials. Another factor would likely be any wiping contact with the coating during cleaning.
In addition to being unsightly, the flaking of the coating allows light to pass through the glass substrate producing a glaring out the back side of the reflector. The resulting loss of light is disadvantageous because onlookers from the rear side of the lamp are met with an intense glare and useful light intensity is diminished in the forward direction. This problem is presently dealt with by recoating the back surface of the glass substrate with another dichroic coating layer and a protective paint coating thereon. This, however, is done at considerable expense and works only until such time as the new coating begins to flake off.
One advance over the known paint coating on the rear surface of the glass substrate has been the use of a reflector in which the dichroic coating is applied on the front surface of the glass substrate and the rear surface thereof is covered with a ceramic frit material. However, the ceramic frit coating also appears to be prone to chipping, peeling, or flaking after some period of reflector use.
An additional problem with the PTFE paint coating on the glass substrate rear surface is that whereas the rest of the dental operatory facility can be sterilized with a conventional sterilant wipe liquid, the substrate rear surface, which usually is also the back surface of the reflector, is not so sterilized. In this regard, the instructions for use of the conventional reflector state that the back surface of the glass substrate should not be cleaned with anything other than a dry cloth so that the coating on the substrate rear surface is not damaged, abraded away or washed away by the sterilization.
Accordingly, it has been considered desirable to develop a new and improved reflector which would overcome the foregoing difficulties and others and meet the above-stated needs while providing better and more advantageous overall results.